Ans. is 'b' i.e., Allodynia o Stages of anaesthesia are Stage of analgesia ( stage 1), stage of delirium or excitment (stage 2), stage of surgical anesthesia (stage 3) and stage of medullary'- paralysis (stage 4).o Guedel described four stages of ether anesthesia known as Guedel stages.Stages of anaesthesiao GAs cause an irregular descending depression of the CNS, i.e., higher functions are lost first and pregressively lower area of brain are involved. In spinal cord lower segments are affected earlier than upper segments. The vital centers located in the medulla are paralyzed the last as the depth of anaesthesia increases,o Guedel discribed four stages of ether anaesthesia dividing the Illrd stage into 4 planes. With faster acting GAs these clear cut stages are not seen nowr days as induction with these agents is too fast. Stage 1 (Stage of analgesia): - It extends from beginning of anaesthetic inhalation to the loss of conciousness. Stage 2 (Stage of delirium or excitment): - From the loss of conciousness to beginning of regular respiration. There is roving eye ball (maximum movement of eye). Pupil is partially dilated. Eye lashr eflex is lost - First reflex to be lost However eyelid reflex remains present.C) Stage 3 ( stage of surgical anaesthesia): - From beginning of regular respiration to cessation of spontaneous breathing. Most surgeries are done in this stage. It is divided into 4 planes : -Plane 1 : - From beginning of regular respiration to cessation of eye movement. There is roving eye ball. Eye lid reflex is lost. This plane ends when eye ball become fixed. Pupil size is normal.Plane 2 : - From cessation of eye movement to respiratory Paresis. Eye ball is fixed. There is loss of corneal reflex.Pupil starts dilating ( 1/2 dilated).Plane 3 : - From respiratory paresis to respiratoy' paralysis. Pupil 3/4 dilated. Swallowing reflex and laryngeal reflexes are tost.Plane 4 : - Intercostal paralysis, there is only abdominal respiration. Pupil is fully dilated. Carinal reflex (Cough reflex) is lost - Last reflex to be lostLacrimation is present in plane II & III and absent in Plane III, IV.D) Stage 4 (stage of medullary paralysis): - There is respiratory arrest and apnea. Pupil is fully dilated & fixed.